The invention relates to a device unit for positioning and causing rotation of a disk provided with a central hole for purposes of reading and/or writing of information on said disk, and particularly to a drive unit for use with an optical disk of the type known by the title "Compact Disc".
There exist manually-loaded readers, in which the user places the disk directly on a turntable intended to rotate it for reading, and drawer-loading readers, in which the user places the disk on a horizontal support belonging to a drawer which may for this purpose move out of the reader by means of a horizontal movement, the turntable taking over the disk and removing it from this support by means of a pivotal movement about a horizontal axis, after closure of the drawer.
In both categories of readers, means comprising a magnet are provided in order to connect the disk with the turntable. Moreover, reading of information is effected by a reading head which is displaced substantially radially with respect to one face of the disk. As the distance between the reading head and the surface of the disk must be precisely defined, the head is mounted on a guide structure which is itself integral with the turntable and which, in the case of a drawer reader, accompanies it in its pivotal movement.
It is theoretically possible to use the same head for uninterrupted and alternating reading of disks placed on different turntables, each disk placed on a turntable being replaced after reading and during reading of a disk placed on another turntable. However, manual positioning of the disk in the case of a manually-loaded reader, and its securement by magnetic means, for both types of readers, cause shock and vibration which could then be transmitted to the reading head and disturb the ongoing reading process. In drawer readers, the pivotal movement of the head with the turntable likewise prevents it from functioning during changeover of the disk.
Moreover, the pivotal movement of the turntable, in the case of a drawer reader, and the magnetic fixing of the disk, use a motor separate from the one used for causing rotation of the turntable during reading; this complicates the structure of the arrangement and increases its bulk and its expense.